The present invention relates to a vehicle rotating electric machine to be mounted on a vehicle.
For the purpose of improving fuel consumption and reducing an exhaust emission including carbon dioxide, in vehicles, there has been proposed an idling stop system for stopping an engine temporarily when the automobile are stopping such as waiting at a red light. The idling stop system provides an engine start system including, for example, a motor and an inverter device, separately from a starter. In this type, the motor is disposed in proximity to the engine, and transmits a driving force to the engine through a clutch and a belt at the time of restarting the engine. On the other hand, since the inverter device has a large number of electronic parts that are low in the durability at high temperature, it is necessary that the inverter device is separated and arranged at a position that avoids a high temperature environment in the vicinity of the engine. For that reason, additional parts such as the inverter device and the electric cable that connects the inverter device and the motor are disposed within an engine room having a limited space, and the idling stop system cannot be mounted without changing the layout of the interior of the engine room.
From the above viewpoint, a motor and an inverter device able to be simply mounted and low in the costs have been demanded for spread of the idling stop system. As one solution to the above demand, there has been proposed an alternator (hereinafter also referred to as “inverter built-in alternator”) which is equipped with a three-phase bridge converter circuit using MOS (metal oxide semiconductor) elements and a control circuit for the three-phase bridge converter circuit to enable motor drive. The inverter built-in alternator has an Inverter circuit in which a rectifier diode of a normal vehicle alternator is replaced by a MOS element. Since the inverter built-in alternator can be realized by the substantially same size as that of the normal vehicle alternator, the idling stop system can be realized without remarkably changing the layout of the interior of the engine room even in a small vehicle having a limited mounting space. Documents of the prior arts are as follows.    [Document 1] Japanese Patent Laid-Open No. 2002-89417    [Document 2] Japanese Patent Laid-Open No. H6(1994)-225476    [Document 3] Japanese Patent Laid-Open No. H7(1995)-75262    [Document 4] Japanese Patent Laid-Open No. 2003-70256
In the inverter circuit equipped in the inverter built-in alternator, downsizing of the device and having the durability at a high temperature are required to enable to arrange the device concerning the inverter in a high temperature environment in the vicinity of the engine. However, because the conventional large current output inverter has the three-phase bridge converter circuit made up of an N-channel MOSFET (metal oxide semiconductor field effect transistor) which is low in the on-resistance, there is provided a wiring layout in which the MOSFET at the higher side and the MOSFET at the lower side are connected to conductor plates that are different in the potential. As a result, because the two conductor plates thus insulated are required, the inverter circuit is prevented from being downsized. Also, because the potential of the output terminal of the bridge circuit fluctuates roughly from the power potential to the ground potential according to the on/off states of the semiconductor switches at the higher side and the lower side, a power supply that provides a reference potential as the output terminal potential is required in the driver circuit of the MOSFET at the higher side in each of the phases (refer to FIG. 15). A large-capacity electrolytic capacitor is essential for the power supply of the driver circuit of the high-side MOSFET in order to hold the voltage. However, the electrolytic capacitor is larger in the volume than other electronic parts, and has such a characteristic that the electrostatic capacity is reduced and the deterioration such as an increase of the internal resistor is liable to occur under the high temperature environment. As a result, it is difficult to realize the inverter built-in alternator that requires the downsizing and the high-temperature durability in the inverter circuit that requires the electrolytic capacitor.
Also, the inverter built-in alternator requires the driver circuit, the minimum control circuits, a protector circuit and power supplies for those circuits in addition to the field current control circuit that is equipped in the conventional alternator having only a power generating function. However, in the case where the respective circuits are made up of the individual parts, it is very difficult from the viewpoint of sizes to realize that those circuits are equipped in the inverter built-in alternator. In addition, there is required that each of those circuits is made up of a circuit or a power supply which does not require the electrolytic capacitor from the viewpoint of the high-temperature resistant durability.